body {
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f0f0f0;
}

.btn {
    border-radius: 5px !important;
}

canvas {
    border-radius: 15px;
    border: 4px solid #000;
    transition: all .5s;
}